//
// Description : Array and textureless GLSL 3D simplex noise function.
//      Author : Ian McEwan, Ashima Arts.
//  Maintainer : ijm
//     Lastmod : 20110409 (stegu)
//     License : Copyright (C) 2011 Ashima Arts. All rights reserved.
//               Distributed under the MIT License. See LICENSE file.
//
uniform float time;
varying vec2 vUv;

vec4 permute( vec4 x ) {
	return mod( ( ( x * 34.0 ) + 1.0 ) * x, 289.0 );
}

vec4 taylorInvSqrt( vec4 r ) {
	return 1.79284291400159 - 0.85373472095314 * r;
}

float snoise( vec3 v ) {
	const vec2 C = vec2( 1.0 / 6.0, 1.0 / 3.0 );
	const vec4 D = vec4( 0.0, 0.5, 1.0, 2.0 );
	// First corner
	vec3 i  = floor( v + dot( v, C.yyy ) );
	vec3 x0 = v - i + dot( i, C.xxx );
	// Other corners
	vec3 g = step( x0.yzx, x0.xyz );
	vec3 l = 1.0 - g;
	vec3 i1 = min( g.xyz, l.zxy );
	vec3 i2 = max( g.xyz, l.zxy );
	vec3 x1 = x0 - i1 + 1.0 * C.xxx;
	vec3 x2 = x0 - i2 + 2.0 * C.xxx;
	vec3 x3 = x0 - 1. + 3.0 * C.xxx;
	// Permutations
	i = mod( i, 289.0 );
	vec4 p = permute( permute( permute(
			 i.z + vec4( 0.0, i1.z, i2.z, 1.0 ) )
		   + i.y + vec4( 0.0, i1.y, i2.y, 1.0 ) )
		   + i.x + vec4( 0.0, i1.x, i2.x, 1.0 ) );
	// Gradients
	// ( N*N points uniformly over a square, mapped onto an octahedron.)
	float n_ = 1.0 / 7.0; // N=7
	vec3 ns = n_ * D.wyz - D.xzx;
	vec4 j = p - 49.0 * floor( p * ns.z *ns.z );  //  mod(p,N*N)
	vec4 x_ = floor( j * ns.z );
	vec4 y_ = floor( j - 7.0 * x_ );    // mod(j,N)
	vec4 x = x_ *ns.x + ns.yyyy;
	vec4 y = y_ *ns.x + ns.yyyy;
	vec4 h = 1.0 - abs( x ) - abs( y );
	vec4 b0 = vec4( x.xy, y.xy );
	vec4 b1 = vec4( x.zw, y.zw );
	vec4 s0 = floor( b0 ) * 2.0 + 1.0;
	vec4 s1 = floor( b1 ) * 2.0 + 1.0;
	vec4 sh = -step( h, vec4( 0.0 ) );
	vec4 a0 = b0.xzyw + s0.xzyw * sh.xxyy;
	vec4 a1 = b1.xzyw + s1.xzyw * sh.zzww;
	vec3 p0 = vec3( a0.xy, h.x );
	vec3 p1 = vec3( a0.zw, h.y );
	vec3 p2 = vec3( a1.xy, h.z );
	vec3 p3 = vec3( a1.zw, h.w );
	// Normalise gradients
	vec4 norm = taylorInvSqrt( vec4( dot( p0, p0 ), dot( p1, p1 ), dot( p2, p2 ), dot( p3, p3 ) ) );
	p0 *= norm.x;
	p1 *= norm.y;
	p2 *= norm.z;
	p3 *= norm.w;
	// Mix final noise value
	vec4 m = max( 0.6 - vec4( dot( x0, x0 ), dot( x1, x1 ), dot( x2, x2 ), dot( x3, x3 ) ), 0.0 );
	m = m * m;
	return 42.0 * dot( m*m, vec4( dot( p0, x0 ), dot( p1, x1 ),
								  dot( p2, x2 ), dot( p3, x3 ) ) );
}

float surface3( vec3 coord ) {
	float n = 0.0;
	n += 1.0 * abs( snoise( coord ) );
	n += 0.5 * abs( snoise( coord * 2.0 ) );
	n += 0.25 * abs( snoise( coord * 4.0 ) );
	n += 0.125 * abs( snoise( coord * 8.0 ) );
	return n;
}

void main( void ) {
	vec3 coord = vec3( vUv, -time );
	float n = surface3( coord );
	gl_FragColor = vec4( vec3( n, n, n ), 1.0 );
}